Improve PythonRepl.run_async() method

[vxgmichel]

I noticed that the PythonRepl.run_async() method is not equivalent to PythonRepl.run(), even though it should behave the same according to the code in ptpython.repl.embed:

ptpython/ptpython/repl.py

Lines 369 to 378 in 89017ba

	if return_asyncio_coroutine:
	async def coroutine():
	with patch_context:
	await repl.run_async()
	return coroutine()
	else:
	with patch_context:
	repl.run()

This is part of my work on prompt-toolkit/python-prompt-toolkit#1150

Note: f1c4906 is entirely optional

[jonathanslenders]

Thank you!

[davidmoss]

This change causes django.core.exceptions.SynchronousOnlyOperation: You cannot call this from an async context - use a thread or sync_to_async. when used with shell_plus. I know this can be suppressed with DJANGO_ALLOW_ASYNC_UNSAFE=True but the question is was this expected?